The invention relates to methods and compositions for inhibiting certain aspartyl proteases. More particularly it relates to methods and compounds for inhibiting the enzymatic activity of secretases involved in converting amyloid precursor protein to amyloid-xcex2 peptide. The methods and compounds of the invention can be used in the treatment of neurodegenerative disorders, notably Alzheimer""s disease.
Accumulating biochemical, histological, and genetic evidence supports the hypothesis that the 4 kDa xcex2-amyloid protein (Axcex2) is an essential component in the pathogenesis of Alzheimer""s disease (AD). Selkoe D J, Science 275:630-631 (1997). Hardy J, Proc Natl Acad Sci USA 94:2095-2097 (1997). Despite the intense interest in the role of Axcex2 in the etiology of AD, the molecular mechanism of Axcex2 biosynthesis is poorly understood. The 39-43-residue Axcex2 is formed via the sequential cleavage of the integral membrane amyloid precursor protein (APP) by xcex2- and xcex3-secretases. Selkoe D J, Annu Rev Cell Biol 10:373-403 (1994). xcex2-Secretase cleavage of APP occurs near the membrane, producing the soluble APP8-xcex2 and a 12 kDa C-terminal membrane-associated fragment (CTF). The latter is processed by xcex3-secretase, which cleaves within the transmembrane domain of the substrate to generate Axcex2. An alternative proteolytic event carried out by xcex1-secretase occurs within the Axcex2 portion of APP, releasing APP8-xcex1, and subsequent processing of the resulting membrane-bound 10 kDa CTF by xcex3-secretase leads to the formation of a 3 kDa N-terminally truncated version of Axcex2 called p3.
Heterogeneous proteolysis of the 12 kDa CTF by xcex3-secretase generates primarily two C-terminal variants of Axcex2, 40- and 42-amino acid versions (Axcex240 and Axcex242), and parallel processing of the 10 kDa CTF generates the corresponding C-terminal variants of p3. Although Axcex242 represents only about 10% of secreted Axcex2, this longer and more hydrophobic variant is disproportionally present in the amyloid plaques observed post mortem in AD patients (Roher A E et al., Proc Natl Acad Sci USA 90:10836-40 (1993); Iwatsubo T et al., Neuron 13:45-53 (1994)), consistent with in vitro studies illustrating the kinetic insolubility of Axcex242 vis-xc3xa1-vis Axcex240. Jarrett J T et al., Biochemistry 32:4693-4697 (1993). Importantly, all genetic mutations associated with early-onset ( less than 60 years) familial Alzheimer""s disease (FAD) result in increased Axcex242 production. Selkoe D J, Science 275:630-631 (1997); Hardy J, Proc Natl Acad Sci USA 94:2095-2097 (1997). An understanding of the production of Axcex2 in general and that of Axcex242 in particular is essential for elucidating the molecular mechanism of AD pathogenesis and may also lead to the development of new chemotherapeutic agents which strike at the etiological heart of the disease.
Both xcex3-secretase and xcex2-secretase are attractive targets for inhibitor design for the purpose of inhibiting production of Axcex2. While xcex3-secretase is an attractive target for inhibitor design, little is known about the structure, mechanism, or binding requirements of this unidentified protease.
In view of the foregoing, a need still exists to develop compositions and methods for treating disorders characterized by the production and deposition of xcex2-amyloid.
The present invention relates to novel compounds useful for inhibiting certain aspartyl proteases, particularly those involved in generating xcex2-amyloid from APP. The compounds are useful for treating a subject having or at risk of having a xcex2-amyloid-associated disease.
In a first aspect, the invention provides novel compounds of Formula I 
wherein R1 is selected from the group consisting of hydrogen, alkyl, cycloalkyl, aromatic, heteroaromatic, R6O(Cxe2x95x90O), and R7R8N(Cxe2x95x90O), wherein R6, R7, and R8 are independently selected from the group consisting of hydrogen, alkyl, cycloalkyl, aromatic, and heteroaromatic, provided R1 is not bonded to the Formula I nitrogen via a group 
wherein Z is C and X is O, S, or N; R2 and R3 are each independently selected from the group consisting of hydrogen, alkyl, cycloalkyl, aromatic, and heteroaromatic; NHxe2x80x94R4 is peptidyl or R4 is independently selected from the group consisting of hydrogen, alkyl, cycloalkyl, aromatic, and heteroaromatic; and non-hydrogen R1, R2, R3, R4, R6, R7, and R8 can independently be substituted with alkylamino, alkoxy, amino, halide, nitro, sulfate, sulfonamide, sulfoxide, or thiol ether.
In some preferred embodiments R1 is t-butyloxycarbonyl (Boc).
In these and other preferred embodiments R2 is bulky and is selected from the group consisting of cyclohexyl, benzyl and other amino acid side chains. In a more preferred embodiment R2 is benzyl, i.e., the side chain of phenylalanine.
In these and other preferred embodiments R3 is selected from the group consisting of methyl, isopropyl, isobutyl, benzyl and other amino acid side chains. In a more preferred embodiment R3 is benzyl, i.e., the side chain of phenylalanine. Also in these and other preferred embodiments R3 is selected from the group consisting of the side chains of alanine, leucine, and valine.
In these and other preferred embodiments NH-R4 is selected from the group consisting of alanine-phenylalanine O-methyl ester, leucine-alanine O-methyl ester, leucinexe2x80x94leucine O-methyl ester, leucine-phenylalanine O-methyl ester, leucine-valine O-methyl ester, and valine-phenylalanine O-methyl ester. In some preferred embodiments NHxe2x80x94R4 is selected from the group consisting of leucine-valine-alanine O-methyl ester, leucine-valine-leucine O-methyl ester, leucine-valine-phenylalanine O-methyl ester, and leucine-valinexe2x80x94valine O-methyl ester.
In one particularly preferred embodiment R1 is t-butyloxycarbonyl; R2 is benzyl; R3 is benzyl; and NHxe2x80x94R4 is leucinexe2x80x94leucine O-methyl ester.
In another particularly preferred embodiment R1 is t-butyloxycarbonyl; R2 is benzyl; R3 is isobutyl; and NHxe2x80x94R4 is leucinexe2x80x94leucine O-methyl ester.
In another particularly preferred embodiment R1 is t-butyloxycarbonyl; R2 is benzyl; R3 is benzyl; and NHxe2x80x94R4 is alanine-phenylalanine O-methyl ester.
In another particularly preferred embodiment R1 is t-butyloxycarbonyl; R2 is benzyl; R3 is benzyl; and NHxe2x80x94R4 is leucine-valine O-methyl ester.
In another particularly preferred embodiment R1 is t-butyloxycarbonyl; R2 is benzyl; R3 is benzyl; and NHxe2x80x94R4 is valine-phenylalanine O-methyl ester.
In another particularly preferred embodiment R1 is t-butyloxycarbonyl; R2 is benzyl; R3 is benzyl; and NHxe2x80x94R4 is leucine-valine-phenylalanine O-methyl ester.
According to this aspect of the invention, certain embodiments embrace a stereoisomer of the compound of Formula I. Other related embodiments embrace a mixture of different stereoisomers of the compound of Formula I. In certain preferred embodiments all stereocenters are R.
Yet another embodiment is a pharmaceutically acceptable salt of the compound of Formula I.
Also provided according to this aspect of the invention is a pharmaceutical composition comprising a compound of Formula I and further comprising a pharmaceutically acceptable carrier. Preferably the pharmaceutically acceptable carrier is adapted for oral administration of a compound of Formula I to a subject. More preferably the pharmaceutically acceptable carrier is adapted for promoting delivery of a compound of Formula I to a brain of a subject.
The invention also provides a method for making a pharmaceutical composition. The method comprises placing a compound of Formula I according to this aspect of the invention in a pharmaceutically acceptable carrier. The method specifically embraces placing the above-identified preferred embodiments of the compound of Formula I in a pharmaceutically acceptable carrier.
In a second aspect the invention provides novel compounds of Formula I 
wherein R1 is selected from the group consisting of hydrogen, alkyl, cycloalkyl, aromatic, heteroaromatic, acyl (R5Cxe2x95x90O), R6(Cxe2x95x90O), and R7R8N(Cxe2x95x90O), wherein R5, R6, R7, and R8 are independently selected from the group consisting of hydrogen, alkyl, cycloalkyl, aromatic, and heteroaromatic; R2 and R3 are each independently selected from the group consisting of hydrogen, alkyl, cycloalkyl, aromatic, and heteroaromatic; NHxe2x80x94R4 is peptidyl or R4 is independently selected from the group consisting of hydrogen, alkyl, cycloalkyl, aromatic, and heteroaromatic; R5 is selected from the group consisting of hydrogen, alkyl, cycloalkyl, aromatic, and heteroaromatic; andnon-hydrogen R1, R2, R3, R4, and R5 can independently be substituted with alkylamino, alkoxy, amino, halide, nitro, sulfate, sulfonamide, sulfoxide, or thiol ether.
Preferred embodiments specifically exclude compounds previously disclosed in Getman DP et al., J Med Chem 36:288-291 (1993). Thus, preferred embodiments according to this aspect of the instant invention exclude compounds having Formula I, in which (using the convention of Formula I above) R2 is benzyl and R1 is xe2x80x94COxe2x80x94CH(NHR)CH2CONH2, wherein:
R is carbobenzyloxy, R3 is methyl, and R4 is methyl;
R is carbobenzyloxy, R3 is methyl, and R4 is n-butyl;
R is carbobenzyloxy, R3 is isobutyl, and R4 is methyl;
R is carbobenzyloxy, R3 is isobutyl, and R4 is n-butyl;
R is quinolinyl-2-carboxamide, R3 is isobutyl, and R4 is n-butyl;
R is carbobenzyloxy, R3 is isobutyl, and R4 is n-propyl;
R is carbobenzyloxy, R3 is isobutyl, and R4 is ethyl;
R is carbobenzyloxy, R3 is isobutyl, and R4 is isopropyl;
R is carbobenzyloxy, R3 is isobutyl, and R4 is tert-butyl;
R is quinolinyl-2-carboxamide, R3 is isobutyl, and R4 is tert-butyl;
R is carbobenzyloxy, R3 is isopentyl, and R4 is tert-butyl;
R is quinolinyl-2-carboxamide, R3 is isopentyl, and R4 is tert-butyl;
R is carbobenzyloxy, R3 is CH2C6H11, and R4 is tert-butyl;
R is quinolinyl-2-carboxamide, R3 is CH2C6H11, and R4 is tert-butyl;
R is carbobenzyloxy, R3 is benzyl, and R4 is tert-butyl;
R is quinolinyl-2-carboxamide, R3 is benzyl, and R4 is tert-butyl;
R is carbobenzyloxy, R3 is (R)xe2x80x94CH(CH3)-phenyl, and R4 is tert-butyl;
R is carbobenzyloxy, R3 is (S)xe2x80x94CH(CH3)-phenyl, and R4 is tert-butyl;
R is carbobenzyloxy, R3 is CH2(4-pyridyl), and R4 is tert-butyl; or
R is quinolinyl-2-carboxamide, R3 is CH2(4-pyridyl), and R4 is tert-butyl.
Preferred embodiments also specifically exclude compounds SC-52151 and SC-55389A previously disclosed in Bryant M et al., Antimicrob Agents Chemother 39:2229-2234 (1995) and Smidt M L et al., Antimicrob Agents Chemother 41:515-522 (1997). Thus, preferred embodiments according to this aspect of the instant invention exclude compounds having Formula I, in which (using the convention of Formula I above) R1 is xe2x80x94COxe2x80x94CH(C(CH3)3)NHR wherein R is COCH2NHCH3 HCl, R2 is benzyl, R3 is isopentyl, and R4 is tert-butyl.
Preferred embodiments also specifically exclude compounds disclosed in U.S. Pat. No. 5,457,013 (issued to Talley et al.). Thus, preferred embodiments according to this aspect of the invention exclude compounds having Formula I in which R1 is a radical represented by any of the formulas A1, A2, A3 below: 
wherein:
R14 represents hydrogen and alkoxycarbonyl, aralkoxycarbonyl, alkylcarbonyl, cycloalkylcarbonyl, cycloalkylalkoxycarbonyl, cycloalkylalkanoyl, alkanoyl, aralkanoyl, aroyl, aryloxycarbonyl, aryloxyalkanoyl, heterocyclylcarbonyl, heterocyclyloxycarbonyl, heterocyclylalkanoyl, heterocyclylalkoxycarbonyl, heteroaralkoxycarbonyl, heteroaryloxycarbonyl, heteroaralkanoyl, heteroaroyl, alkyl, aryl, aralkyl, aryloxyalkyl, heteroaryloxyalkyl, hydroxyalkyl, aminocarbonyl, aminoalkanoyl, and mono- and disubstituted aminocarbonyl and mono- and disubstituted aminoalkanoyl radicals wherein the substituents are selected from alkyl, aryl, aralkyl, cycloalkyl, cycloalkylalkyl, heteroaryl, heteroaralkyl, heteroalkyl and heterocycloalkylalkyl radicals or in the case of a disubstituted aminoalkanoyl radical, said substitutents along with the nitrogen atom to which they are attached form a heterocycloalkyl or heteroaryl radical;
R12 represents hydrogen and radicals as defined for R13 or R14 and R12 together with the nitrogen to which they are attached form a heterocycloalkyl or heteroaryl radical or when R1 is A1, R12 represents hydrogen, radicals as defined for R13 and aralkoxycarbonylalkyl and aminocarbonylalkyl and aminoalkyl radicals wherein said amino group may be mono- or disubstituted with substituents selected from alkyl, aryl, aralkyl, cycloalkyl, cycloalkylalkyl, heteroaryl, heteroaralkyl, heteroalkyl, and heterocycloalkylalkyl radicals;
t represents either 0 or 1;
R9 represents hydrogen, xe2x80x94CH2SO2NH2, xe2x80x94CO2CH3, xe2x80x94CH2CO2CH3, xe2x80x94CONH2, xe2x80x94CH2C(O)NHCH3, xe2x80x94CH2C(O)N(CH3)2, xe2x80x94CONHCH3, xe2x80x94CONH(CH3)2, xe2x80x94C(CH3)2(SCH3), xe2x80x94C(CH3)2(S[O]CH3), xe2x80x94C(CH3)2(S[O]2CH3), alkyl, haloalkyl, alkenyl, alkynyl and cycloalkyl radicals and amino acid side chains selected from asparagine, S-methyl cysteine and the corresponding sulfoxide and sulfone derivatives thereof, glycine, leucine, isoleucine, alloisoleucine, tert-leucine, phenylalanine, omithine, alanine, histidine, norleucine, glutamine, valine, threonine, serine, aspartic acid, beta-cyano alanine, and allo-threonine side chains;
R15 and R16 independently represent hydrogen and radicals as defined for R9, or one of R15 and R16, together with R9 and the carbon atoms to which they are attached, represent a cycloalkyl radical;
R13 represents alkyl, alkenyl, alkynyl, hydroxyalkyl, alkoxyalkyl, cycloalkyl, cycloalkylalkyl, heterocycloalkyl, heteroaryl, heterocycloalkylalkyl, aryl, aralkyl, heteroaralkyl, aminoalkyl and mono- and disubstituted aminoalkyl radicals where said substitutents are selected from alkyl, aryl, aralkyl, cycloalkyl, cycloalkylalkyl, heteroaryl, heteroalkyl, heterocycloalkyl, and heterocycloalkylalkyl radicals or, in the case of a disubstituted aminoalkanoyl radical, said substituents along with the nitrogen atom to which they are attached, form a heterocycloalkyl or a heteroaryl radical;
Xxe2x80x2 represents O C(R21) where R21 represents hydrogen and alkyl radicals and N;
Yxe2x80x2 and Yxe2x80x3 independently represent O, S and NR20 wherein R20 represents hydrogen and radicals as defined for R13;
R10, R11, R17, R18 and R19 represent radicals as defined for R9, or one of R9 and R17 together with one of R18 and R19 and the carbon atoms to which they are attached form a cycloalkyl radical; and
R22 and R23 independently represent hydrogen and radicals as defined for R13, or R22 and R23 together with Xxe2x80x2 represent cycloalkyl, aryl, heterocyclyl and heteroaryl radicals, provided that when Xxe2x80x2 is O, R23 is absent.
In these and other preferred embodiments R2 is bulky and is selected from the group consisting of cyclohexyl, benzyl and other amino acid side chains. In a more preferred embodiment R2 is benzyl, i.e., the side chain of phenylalanine.
In these and other preferred embodiments R3 is selected from the group consisting of methyl, isopropyl, isobutyl, benzyl and other amino acid side chains. In a more preferred embodiment R3 is benzyl, i.e., the side chain of phenylalanine. Also in these and other preferred embodiments R3 is selected from the group consisting of the side chains of alanine, leucine, and valine.
In these and other preferred embodiments NHxe2x80x94R4 is selected from the group consisting of alanine-phenylalanine O-methyl ester, leucine-alanine O-methyl ester, leucinexe2x80x94leucine O-methyl ester, leucine-phenylalanine O-methyl ester, leucine-valine O-methyl ester, and valine-phenylalanine O-methyl ester. In some preferred embodiments NHxe2x80x94R4 is selected from the group consisting of leucine-valine-alanine O-methyl ester, leucine-valine-leucine O-methyl ester, leucine-valine-phenylalanine O-methyl ester, and leucine-valinexe2x80x94valine O-methyl ester.
In one particularly preferred embodiment R1 is t-butyloxycarbonyl; R2 is benzyl; R3 is benzyl; and NHxe2x80x94R4 is leucinexe2x80x94leucine O-methyl ester.
In another particularly preferred embodiment R1 is t-butyloxycarbonyl; R2 is benzyl; R3 is isobutyl; and NHxe2x80x94R4 is leucinexe2x80x94leucine O-methyl ester.
In another particularly preferred embodiment R1 is t-butyloxycarbonyl; R2 is benzyl; R3 is benzyl; and NHxe2x80x94R4 is alanine-phenylalanine O-methyl ester.
In another particularly preferred embodiment R1 is t-butyloxycarbonyl; R2 is benzyl; R3 is benzyl; and NHxe2x80x94R4 is leucine-valine O-methyl ester.
In another particularly preferred embodiment R1 is t-butyloxycarbonyl; R2 is benzyl; R3 is benzyl; and NHxe2x80x94R4 is valine-phenylalanine O-methyl ester.
In another particularly preferred embodiment R1 is t-butyloxycarbonyl; R2 is benzyl; R3 is benzyl; and NHxe2x80x94R4 is leucine-valine-phenylalanine O-methyl ester.
According to this aspect of the invention, certain embodiments embrace a stereoisomer of the compound of Formula I. Other related embodiments embrace a mixture of different stereoisomers of the compound of Formula I. In certain preferred embodiments all stereocenters are R.
Yet another embodiment is a pharmaceutically acceptable salt of the compound of Formula I.
Also provided is a pharmaceutical composition comprising a compound of Formula I and further comprising a pharmaceutically acceptable carrier. Preferably the pharmaceutically acceptable carrier is adapted for oral administration of a compound of Formula I to a subject. More preferably the pharmaceutically acceptable carrier is adapted for promoting delivery of a compound of Formula I to a brain of a subject.
The invention according to this aspect also provides a method for making a pharmaceutical composition. The method comprises placing a compound of Formula I according to this aspect of the invention in a pharmaceutically acceptable carrier. The method specifically embraces placing the above-identified preferred embodiments of the compound of Formula I in a pharmaceutically acceptable carrier.
In a third aspect the invention provides a method for treating a subject having or at risk of having a xcex2-amyloid-associated disease. The method according to this aspect of the invention involves administering to a subject having or at risk of having a xcex2-amyloid-associated disease a therapeutically effective amount of a compound of Formula I according to the first aspect or second aspect of the invention as described above.
A compound of Formula I as used throughout this application shall refer to a compound of Formula I according to the first aspect of the invention as described above or to a compound of Formula I according to the second aspect of the invention as described above. These two aspects differ primarily from one another in the nature of the R1 group. Compounds of a first aspect of the invention have an R1 group which is not bonded to the Formula I nitrogen via a group 
wherein Z is C and X is O, S, or N. Compounds of a second aspect of the invention have an R1 group that can be bonded to the Formula I nitrogen via a group 
wherein Z is C and X is O, S, or N.
In a preferred embodiment the xcex2-amyloid-associated disease is a neurodegenerative disease. In a more preferred embodiment the xcex2-amyloid-associated disease is Alzheimer""s disease.
In certain embodiments the subject is free of symptoms otherwise calling for treatment with a compound of Formula I. Preferably the subject is free of symptoms of retrovirus infection. More preferably the subject is free of symptoms of human immunodeficiency virus (HIV) infection.
According to this aspect of the invention the compound of Formula I is as described above, including preferred embodiments. The compound of Formula I can be packaged in unit dose form for convenience in dosing.
Preferably the compound of Formula I is administered orally.
In some preferred embodiments R1 is t-butyloxycarbonyl.
In these and other preferred embodiments R2 is bulky and is selected from the group consisting of cyclohexyl, benzyl and other amino acid side chains. In a more preferred embodiment R2 is benzyl, i.e., the side chain of phenylalanine.
In these and other preferred embodiments R3 is selected from the group consisting of methyl, isopropyl, isobutyl, benzyl and other amino acid side chains. In a more preferred embodiment R3 is benzyl, i.e., the side chain of phenylalanine. Also in these and other preferred embodiments R3 is selected from the group consisting of the side chains of alanine, leucine, and valine.
In these and other preferred embodiments NHxe2x80x94R4 is selected from the group consisting of alanine-phenylalanine O-methyl ester, leucine-alanine O-methyl ester, leucinexe2x80x94leucine O-methyl ester, leucine-phenylalanine O-methyl ester, leucine-valine O-methyl ester, and valine-phenylalanine O-methyl ester. In some preferred embodiments NHxe2x80x94R4 is selected from the group consisting of leucine-valine-alanine O-methyl ester, leucine-valine-leucine O-methyl ester, leucine-valine-phenylalanine O-methyl ester, and leucine-valinexe2x80x94valine O-methyl ester.
In one particularly preferred embodiment R1 is t-butyloxycarbonyl; R2 is benzyl; R3 is benzyl; and NHxe2x80x94R4 is leucinexe2x80x94leucine O-methyl ester.
In another particularly preferred embodiment R1 is t-butyloxycarbonyl; R2 is benzyl; R3 is isobutyl; and NHxe2x80x94R4 is leucinexe2x80x94leucine O-methyl ester.
In another particularly preferred embodiment R1 is t-butyloxycarbonyl; R2 is benzyl; R3 is benzyl; and NHxe2x80x94R4 is alanine-phenylalanine O-methyl ester.
In another particularly preferred embodiment R1 is t-butyloxycarbonyl; R2 is benzyl; R3 is benzyl; and NHxe2x80x94R4 is leucine-valine O-methyl ester.
In another particularly preferred embodiment R1 is t-butyloxycarbonyl; R2 is benzyl; R3 is benzyl; and NHxe2x80x94R4 is valine-phenylalanine O-methyl ester.
In another particularly preferred embodiment R1 is t-butyloxycarbonyl; R2 is benzyl; R3 is benzyl; and NHxe2x80x94R4 is leucine-valine-phenylalanine O-methyl ester.
According to this aspect of the invention, certain embodiments embrace a stereoisomer of the compound of Formula I. Other related embodiments embrace a mixture of different stereoisomers of the compound of Formula I. In certain preferred embodiments all stereocenters are R.
According to one embodiment of this aspect of the invention, a compound of Formula I is administered to the subject in combination with an effective amount of another agent useful in the treatment of xcex2-amyloid-associated disease. The method thus embraces the administration of a compound of Formula I in combination with an acetylcholinesterase inhibitor. In other embodiments a compound of Formula I is administered in combination with a compound of Formula II 
wherein R1 is selected from the group consisting of hydrogen, alkyl, cycloalkyl, aromatic, heteroaromatic, acyl (R5Cxe2x95x90O), R6O(Cxe2x95x90O), and R7R8N(Cxe2x95x90O), wherein R5, R6, R7, and R8 are independently selected from the group consisting of hydrogen, alkyl, cycloalkyl, aromatic, and heteroaromatic; R2 and R3 are each independently selected from the group consisting of hydrogen, alkyl, cycloalkyl, aromatic, and heteroaromatic; NHxe2x80x94R4 is peptidyl or R4 is independently selected from the group consisting of hydrogen, alkyl, cycloalkyl, aromatic, and heteroaromatic; and non-hydrogen R1, R2, R3, R4, R5, R6, R7, and R8 can independently be substituted with alkylamino, alkoxy, amino, halide, nitro, sulfate, sulfonamide, sulfoxide, or thiol ether.
In a fourth aspect the invention provides a method for inhibiting activity of an aspartyl protease. The method involves contacting an aspartyl protease, under conditions in which aspartyl protease is enzymatically active, with a compound of Formula I according to the first aspect or the second aspect of the invention as described above.
In certain preferred embodiments the aspartyl protease is not a retroviral protease. Preferably the aspartyl protease is not HIV protease.
In certain preferred embodiments the aspartyl protease is not renin.
In a preferred embodiment the aspartyl protease is a xcex3-secretase.
In another preferred embodiment the aspartyl protease is a xcex2-secretase.
In a more preferred embodiment the contacting results in a decrease in the generation of amyloid-xcex2 peptide.
In certain embodiments the method according to this aspect of the invention is performed in vitro. In certain embodiments the method according to this aspect of the invention is performed in vivo.
In a fifth aspect the invention provides a method for treating a subject having or at risk of having a xcex2-amyloid-associated disease. The method involves administering to a subject having or at risk of having a xcex2-amyloid-associated disease and free of symptoms otherwise calling for treatment with a compound of Formula IA or Formula IB, a therapeutically effective amount of a compound of Formula IA or Formula IB 
wherein, with respect to Formula IA:
(i) R2 is benzyl and R1 is xe2x80x94COxe2x80x94CH(NHR)CH2CONH2, wherein:
R is carbobenzyloxy, R3 is methyl, and R4 is methyl;
R is carbobenzyloxy, R3 is methyl, and R4 is n-butyl;
R is carbobenzyloxy, R3 is isobutyl, and R4 is methyl;
R is carbobenzyloxy, R3 is isobutyl, and R4 is n-butyl;
R is quinolinyl-2-carboxamide, R3 is isobutyl, and R4 is n-butyl;
R is carbobenzyloxy, R3 is isobutyl, and R4 is n-propyl;
R is carbobenzyloxy, R3 is isobutyl, and R4 is ethyl;
R is carbobenzyloxy, R3 is isobutyl, and R4 is isopropyl;
R is carbobenzyloxy, R3 is isobutyl, and R4 is tert-butyl;
R is quinolinyl-2-carboxamide, R3 is isobutyl, and R4 is tert-butyl;
R is carbobenzyloxy, R3 is isopentyl, and R4 is tert-butyl;
R is quinolinyl-2-carboxamide, R3 is isopentyl, and R4 is tert-butyl;
R is carbobenzyloxy, R3 is CH2C6H11, and R4 is tert-butyl;
R is quinolinyl-2-carboxamide, R3 is CH2C6H11, and R4 is tert-butyl;
R is carbobenzyloxy, R3 is benzyl, and R4 is tert-butyl;
R is quinolinyl-2-carboxamide, R3 is benzyl, and R4 is tert-butyl;
R is carbobenzyloxy, R3 is (R)xe2x80x94CH(CH3)-phenyl, and R4 is tert-butyl;
R is carbobenzyloxy, R3 is (S)xe2x80x94CH(CH3)-phenyl, and R4 is tert-butyl;
R is carbobenzyloxy, R3 is CH2(4-pyridyl), and R4 is tert-butyl; or
R is quinolinyl-2-carboxamide, R3 is CH2(4-pyridyl), and R4 is tert-butyl; or
(ii) R1 is xe2x80x94COxe2x80x94CH(C(CH3)3)NHR, wherein: R is COCH2NHCH3 HCl, R2 is benzyl, R3 is isopentyl, and R4 is tert-butyl; and, with respect to Formula IB,
R1 is a radical represented by any of the formulas A1, A2, A3 below: 
R2 represents alkyl, aryl, cycloalkyl, cycloalkylalkyl and aralkyl radicals, which radicals are optionally substituted with a group selected from xe2x80x94NO2, xe2x80x94OR30, xe2x80x94SR30, and halogen radicals, wherein R30 represents hydrogen and alkyl radicals;
R4 represents radicals represented by the formula: 
wherein n represents an integer of from 0 to 6, R26 and R27 independently represent radicals as defined for R13 and amino acid side chains selected from the group consisting of valine, isoleucine, glycine, alanine, allo-isoleucine, asparagine, leucine, glutamine, and t-butylglycine or R26 and R27 together with the carbon atom to which they are attached form a cycloalkyl radical; and R28 represents cyano, hydroxyl, alkyl, alkoxy, cycloalkyl, aryl, aralkyl, heterocycloalkyl and heteroaryl radicals and radicals represented by the formulas C(O)R29, CO2R29, SO2R29, SR29, CONR29R21, OR29, CF3 and NR29R21 wherein R29 and R21 independently represent hydrogen and radicals as defined for R13 or R29 and R21 together with a nitrogen to which they are attached in the formula xe2x80x94NR29R21 represent heterocycloalkyl and heteroaryl radicals;
R24 represents hydrogen and alkyl radicals;
R25 independently represents hydrogen and radicals as defined by R13; and
R13 represents alkyl, alkenyl, alkynyl, hydroxyalkyl, alkoxyalkyl, cycloalkyl, cycloalkylalkyl, heterocycloalkyl, heteroaryl, heterocycloalkylalkyl, aryl, aralkyl, heteroaralkyl, aminoalkyl and mono- and disubstituted aminoalkyl radicals where said substitutents are selected from alkyl, aryl, aralkyl, cycloalkyl, cycloalkylalkyl, heteroaryl, heteroalkyl, heterocycloalkyl, and heterocycloalkylalkyl radicals or, in the case of a disubstituted aminoalkanoyl radical, said substituents along with the nitrogen atom to which they are attached, form a heterocycloalkyl or a heteroaryl radical; wherein:
R14 represents hydrogen and alkoxycarbonyl, aralkoxycarbonyl, alkylcarbonyl, cycloalkylcarbonyl, cycloalkylalkoxycarbonyl, cycloalkylalkanoyl, alkanoyl, aralkanoyl, aroyl, aryloxycarbonyl, aryloxyalkanoyl, heterocyclylcarbonyl, heterocyclyloxycarbonyl, heterocyclylalkanoyl, heterocyclylalkoxycarbonyl, heteroaralkoxycarbonyl, heteroaryloxycarbonyl, heteroaralkanoyl, heteroaroyl, alkyl, aryl, aralkyl, aryloxyalkyl, heteroaryloxyalkyl, hydroxyalkyl, aminocarbonyl, aminoalkanoyl, and mono- and disubstituted aminocarbonyl and mono- and disubstituted aminoalkanoyl radicals wherein the substituents are selected from alkyl, aryl, aralkyl, cycloalkyl, cycloalkylalkyl, heteroaryl, heteroaralkyl, heteroalkyl and heterocycloalkylalkyl radicals or in the case of a disubstituted aminoalkanoyl radical, said substitutents along with the nitrogen atom to which they are attached form a heterocycloalkyl or heteroaryl radical;
R12 represents hydrogen and radicals as defined for R13 or R14 and R12 together with the nitrogen to which they are attached form a heterocycloalkyl or heteroaryl radical or when R1 is A1, R12 represents hydrogen, radicals as defined for R13 and aralkoxycarbonylalkyl and aminocarbonylalkyl and aminoalkyl radicals wherein said amino group may be mono- or disubstituted with substituents selected from alkyl, aryl, aralkyl, cycloalkyl, cycloalkylalkyl, heteroaryl, heteroaralkyl, heteroalkyl, and heterocycloalkylalkyl radicals;
t represents either 0 or 1;
R9 represents hydrogen, xe2x80x94CH2SO2NH2, xe2x80x94CO2CH3, xe2x80x94CH2CO2CH3, xe2x80x94CONH2, xe2x80x94CH2C(O)NHCH3, xe2x80x94CH2C(O)N(CH3)2, xe2x80x94CONHCH3, xe2x80x94CONH(CH3)2, xe2x80x94C(CH3)2(SCH3), xe2x80x94C(CH3)2(S[O]CH3), xe2x80x94C(CH3)2(S[O]2CH3), alkyl, haloalkyl, alkenyl, alkynyl and cycloalkyl radicals and amino acid side chains selected from asparagine, S-methyl cysteine and the corresponding sulfoxide and sulfone derivatives thereof, glycine, leucine, isoleucine, alloisoleucine, tert-leucine, phenylalanine, omithine, alanine, histidine, norleucine, glutamine, valine, threonine, serine, aspartic acid, beta-cyano alanine, and allo-threonine side chains;
R15 and R16 independently represent hydrogen and radicals as defined for R9, or one of R15 and R16, together with R9 and the carbon atoms to which they are attached, represent a cycloalkyl radical;
Xxe2x80x2 represents O, C(R21) where R21 represents hydrogen and alkyl radicals and N;
Y, Yxe2x80x2 and Yxe2x80x3 independently represent O, S and NR20 wherein R20 represents hydrogen and radicals as defined for R13;
R10, R11, R17, R18 and R19 represent radicals as defined for R9, or one of R9 and R17 together with one of R18 and R19 and the carbon atoms to which they are attached form a cycloalkyl radical; and
R22 and R23 independently represent hydrogen and radicals as defined for R13, or R22 and R23 together with Xxe2x80x2 represent cycloalkyl, aryl, heterocyclyl and heteroaryl radicals, provided that when Xxe2x80x2 is O, R23 is absent, whereby the xcex2-amyloid disease is treated.